It's important to note that the safety was proved with boys between 10 and 18. High dose idebenone is toxic in vitro to brain cells http://www.ncbi.nlm.nih.gov/pubmed/21547417# so this dose may be dangerous to young kids. Remember that it's a drug that also affects the brain in other ways so we should be very carefull with it. Nobody knows nothing about the growing brain and even less in DMD.